The theme of this final work is the quality of signal transmission over fiber optic networks. The work deals with the description and measurement of optical network with reference to quality. The first and the second part describe the architecture and elements of the fiber optic network in our area. The calculation of loss of signal and the measuring of the installations prove the quality of the performance of the optical network. The result of this work is to point out the advantages offered by fiber optic network in relation to today's twisted pair copper wire or wireless transmissions and that on the last part which comes to the final consumer. Today's telecommunications transmission is slowly becoming obsolete and because of this it is a need to turn as quickly as possible to the optical transmission system which has been very little used yet.